This invention relates to an apparatus for detecting and indicating abnormality in an electronic control system for internal combustion engines, and more particularly to an apparatus of this kind which ensures easy identification of the place where abnormality exists when any one of input and output means of the electronic control system is in an abnormal state.
An electronic control system for an internal combustion engine, for instance, an electronic fuel supply control system for electronically controlling the amount of fuel to be supplied to the engine is generally adapted to detect the values of various parameters indicative of operating conditions of the engine, and control the operation of various output means such as a fuel pump and fuel injection valves, on the basis of the detected values of the various engine operation parameters. Conventionally, when abnormality occurs in such electronic control system equipped with various input and output means, to identify or find out the place where such abnormality exists it is generally employed to determine input and output means to be inspected, depending upon the operating condition in which the engine was operating upon occurrence of the abnormality, and upon the intuition of the serviceman, and inspect those means one by one. However, such checking manner requires a great deal of efforts as well as a lot of time to find out the place where abnormality is present. Particularly, abnormality due to bad connections and short circuits cannot be reproduced in a static condition where the engine is in a standing position, making it impossible to find out the abnormality location. Further, there are some abnormalities which cannot be immediately recognized by the driver, even though they badly affect the emission characteristics, fuel consumption, etc. Upon occurrence of such abnormalities, proper measures cannot be taken immediately.